Ooh! Vacuum Tubes Lit With Tri-Colored LEDs

I have just taken possession of a box of the most amazing old vacuum tubes; you will not believe your eyes!

Sit down and prepare to be flabbergasted. I have news so exciting that I can barely bring myself to speak of it. In my earlier blog on my Ultra-Macho Prognostication Engine project, I mentioned the idea of mounting vacuum tubes on top of the engine and then lighting them from underneath with tri-colored LEDs. The following mock-up gives a rough idea as to what I was thinking:

Now, I have a huge bag of non-functional small vacuum tubes I could use, but we really need something more grandiose for this project. Originally, I had toyed with the idea of using the 12-inch-tall antique vacuum tube I have in The Pleasure Dome (my office) as shown below:

When push came to shove, however, I simply could not bring myself to take this little beauty out of its transportation frame. Thus it was that last Friday, on the way into work, I popped into Mock Electronics (a store so amazing that describing it as "An Eclectic Emporium of Electronic Elements" fails to do it justice).

My hope was to find a really large tube to act as the centerpiece of the display, and indeed I found an absolute beauty -- a monster in size, with an outgrowth of glass on one side, jam-packed with strange and wondrous internal structures. The only problem occurred when I turned this beauty over and discovered its $275 price tag. Once I'd regained consciousness, and various nervous twitches and tremors were under control, I moved on to see if there was anything I could actually afford. You can only imagine my surprise and delight to discover a box of rather interesting 500W bulbs (only a few dollars apiece), one of which is shown below:

I should have placed a ruler next to this bulb when I took this image, but I forgot, so you'll just have to take my word that it's approximately 4.5" in diameter. When I arrived at my office, I took this bulb to show to my chum Ivan, and we whipped it onto the test bench and powered it up. At about 21 volts, the filament gives a very satisfying red glow. That's not what we're seeing here, however, because the filament isn’t being powered in the above image.

Observe the faint rainbow-colored lights at the bottom of the bulb -- just where the base of the bulb goes into a hole I cut in the top of a cardboard box, which is acting as a poor man's prototyping platform. For this first test, I connected four of Adafruit's Flora NeoPixels. (These were kindly sent to me some time ago by EE Times Chief Community Editor Caleb Kraft.)

Unfortunately, the above photo doesn’t do this justice. It looks a lot better in real life. Here's a slightly better image with the room's main lights turned off:

Once again, even this image doesn’t really convey what this looks like to the human eye, which is a sort-of aurora borealis-type effect as shown below:

Having said all of this, even though the effect I've achieved thus far is rather tasty, it really doesn’t stand out enough in bright light. This led me to conceive a cunning plan. Have you seen that glass-etching cream you can get from places like Hobby Lobby, Michaels, and Wal-Mart? The idea is that you first apply some sort of stencil to your glass (painter's masking tape will do), and then use this cream to etch the glass leaving a frosted effect as shown below:

This explains why I was to be found roaming around Michaels yesterday purchasing a jar of this cream. My idea is to frost the top and bottom of my bulb, leaving a wide stripe around the middle unfrosted so that we can still see the glowing filament. I think that this frosting will act as a display screen that captures the light from the LEDs and makes the overall effect much more interesting.

In turn, this explains why this morning on the way into work I once again headed down to Mock Electronics to purchase some more of these bulbs to play with, and I did indeed pick up three more (better safe than sorry) as shown below:

I'm still planning on performing my glass-etching experiments this evening, just to see what will happen. I'm sure these bulbs will find a home in future projects. Unfortunately, I have to say that I no longer plan to use them as part of my Ultra-Macho Prognostication Engine. Why? Well, as soon as I walked through the front door, the folks at Mock Electronics said "Guess what we've discovered hidden away in the depths of the store?" And then they whipped out a box of the most amazing old vacuum tubes as shown below:

OMG! Can you imagine what these will look like on top of the Ultra-Macho Prognostication Engine when they are illuminated from inside with tri-colored LEDs. There is a slight problem (isn’t there always?). I don’t want to do anything that could potentially damage these tubes -- not that they are actually capable of performing their original function, you understand, but I don’t want to crack the glass. Fortunately, I do have a cunning plan... which we will discuss in a future column.

In the meantime, what do you think about these new tubes? You have to agree that they are going to look absolutely amazing on top of the Prognostication Engine.

In particular, before you glue anything to glass - or otherwise make any modifications to the bases of these collector's items, you should take a look around to see if you can find any tube sockets to match them.

For myself, I would feel better about modifying the socket ( if that could provide useful effect ) as opposed to risking harm to the tubes.

Although... some of those old ceramic-based sockets could look almost ( though not quite ) as impressive as the tubes, themselves:

According to the Mock Electronics site your big tube is a JAN 450-TH. Doing some Binging I found it equivalent to a VT-108, or replaceable by a HK854H. It's a triode transmitter, air cooled. The specs on the HK458H say its a 450W plate dissipation at 125Mhz. Another site uses a 450-TH in a Class A audio amp rated at 160W.

I've always fantasized about having a vehicle with two or four 10KW or better amps with speakers good to 25 to 30 KHz mounted on arms that I could deploy on each side of a car that's blasting its music so loud I can hear it through their closed windows and mine. Pipe through it a little high-pitched opera or some English Lute Music (sorry, Max, I like the lute but not the high-pitched soprano), let it run while waiting for the stoplight to change, and presto: Revenge!

I always envision the other car crumbling into dust as if it were in a cartoon.

Uh-oh: have you placed your geiger counter near the tube? This link claims that the filament may have some thorium in the tungsten, and it may be radioactive. Is that where you get your glowing personality?

@Cwrobe: Try some frosted scotch tape for the experiment. No damage to any of the tubes and you can approximate what it will look like on the actual tube. I think. :)

I will certainly try that as well -- good idea -- but I'm not sure that will give the same effect as actually etching into the glass (the tape will act as a diffuser, but the etching will scatter the light in a different way).

But don't worry -- I will practice on a big back of small, cheap, broken tubes that I have here in my office. I'm not doing anything to those big tubes until I'm 100% confident that I knwo what the result will be...

Another idea is to etch a band around the bottom of the tube and then put a ring of NeoPixels around -- I'm thinking the etch will get the light into the glass more effectively -- but I'm experimenting with some small, cheap old tubes first to see...

Try some frosted scotch tape for the experiment. No damage to any of the tubes and you can approximate what it will look like on the actual tube. I think. :)